1. Technical Field
The invention lies in the field of optical couplers for optical waveguides and relates to an optical component, a method for manufacturing an optical component and a method for coupling light out of a waveguide structure or into a waveguide structure, according to the preambles of the independent patent claims. The optical components according to the invention may have extensions in the region of a few centimeters to a few meters. Such optical components are mainly required for optical data transmission, and are applied for example in telecommunication, medical technology, sensor technology, in the construction of vehicles and aircraft, in technology relating to industry, buildings and control. Particularly advantageous embodiments are circuit boards which comprise electrical as well as optical structures.
2. Description of the Related Art
Optical waveguides may be manufactured by way of coating a substrate and subsequent photo-lithographic structuring of the layer. Such a manufacturing method is known for example in DE-197′32′506 A1. Accordingly, a layer of fluid, light-sensitive material, for example a UV-curable polymer is deposited on the substrate. The layer is directly written by way of an incoherent light source, in order to form the waveguide structures. The light-sensitive material is selectively exposed and cured by way of the direct writing. The coating material which has not cured is removed after the exposure has been effected. Multimode waveguides and -structures with core widths of approx. 20 μm or more may be manufactured with these methods.
For practical applications the waveguides must be coupled to other components in a low-loss manner, for example a waveguide located on an optical backplane strip to a processor board. This is effected by way of interfaces which may be designed for example as plug elements and contain suitable optical components such as coupling-in or coupling-out mirrors on the waveguide side.
A method for manufacturing waveguides with optical components is known for example from EP-0′911′658 A1. The optical components are attached on a substrate at predefined coupling-out locations, and are embedded in a waveguide layer. The waveguide structure is manufactured by way of direct writing with an incoherent light source after the deposition of the optical components on the substrate Thereafter, the coating material which is has not cured is again removed.
The exact mutual positioning of the waveguide and optical components plays a very significant role for a low-loss coupling-in and coupling-out. Even a shift by a fraction of the core width leads to a considerable reduction of the coupling efficiency, and thus to light losses. Losses of light however must be avoided in optical circuits, since they always reduce the signal-to-noise ratio at the exit. For this reason, many waveguides manufactured according to the method described in EP-0′911′658 A1 become unusable, even if one attempts to carry out the placing of the optical components and the direct writing of the waveguide structure as accurately and as reproducibly as possible. The method thus results in a high rejection rate.
Method for manufacturing optical components are known from the documents WO-000/60392 and U.S. Pat. No. 5,562,838 with which firstly optical components are deposited onto a substrate. Thereafter, positions and alignments of the optical components are measured. Strip waveguides are manufactured on the substrate in dependency on the determined positions and alignments, so that they are exactly aligned with respect to the optical components.
U.S. Pat. No. 5,832,150 discloses a coupler for glass fibers. For its manufacture, ends of a multitude of glass fibers to be coupled are fixed in a housing. The fiber ends together with an end piece of the housing are ground and polished in a manner such that an elongate, flat coupling facing and a cylindrically curved reflecting surface arises at each fiber end. The curved surface defines a line focus which lies somewhat above the coupling facing. A laser diode array may for example be introduced into the line focus. The light beam with an elliptical cross section which is emitted by a laser diode is coupled via the coupling facing into a corresponding glass fiber and is deflected as well as collimated by the cylindrical, reflecting surface, so that it propagates approximately parallel to the fiber axis in the fiber. One disadvantage of this coupler is its complicated manufacture. Furthermore, such a coupler may only be used for optical fibers which are free, but not for waveguide structures which are deposited on a substrate.
Other embodiments of such couplers also exist, but these are mostly individual solutions for certain applications. They are accordingly technically complicated and expensive in manufacture and procurement.
Objects ans Advantages
It is therefore an object of the present invention to create an optical component with an optical coupling element, wherein the optical component with the optical coupling element may preferably be able to be manufactured in a simple and inexpensive manner and with a mass production, and be suitable for many different applications.
It is furthermore the object of the invention to specify a method for the manufacture of optical components, which permits an exact, mutual positioning of the waveguide and of the coupling element. The coupling efficiency is to be optimized by way of this and the light damping in the component is to be reduced to a minimum. One strives for a production which produces as little as possible rejects.
A further object of the invention is to specify methods for coupling light out of a waveguide structure or into a waveguide structure, which may also be carried out with waveguide structures which are deposited on a substrate.
These and other objects will be apparent to those skilled in this art from the following detailed description of a preferred embodiment of the invention. These and other objects are achieved by the coupling element, the optical component, the manufacturing method and the coupling-in and coupling-out method, as defined in the independent patent claims. Advantageous embodiments are specified in the dependent patent claims.